1. Field of the Invention
The present invention relates to a multiscreen display system, a multiscreen display method, a luminance correction method, and programs.
2. Description of the Related Art
As an example of the prior art, in a multiscreen system, an uneven luminance correction circuit for correcting a video signal is provided in an enlarging distributor. The uneven luminance correction circuit is composed of a LUT (Look-Up Table), divides the addresses of the LUT into (n) parts in accordance with the enlarging ratio of the core, and corrects the uneven luminance for each core by means of the LUT data that have been divided into (n) portions (Japanese Patent Laid-Open Publication No. 50795/95). The following explanation regards the luminance correction method of the prior art with reference to FIG. 1.
In FIG. 1 (1), in order to make uniform the luminance distribution of the areas in which the image displays that are projected by each projector overlap, a means is adopted in the method of the prior art for reducing the luminance levels of the overlapping portions as the edges of the image are approached, and gradation conversion coefficients are determined according to the distance from the image edges. As a method of the prior art for reducing unevenness in luminance in overlapping areas when optical distortion occurs, gradation conversion of the overlapping areas is carried out after first passing the image through an image distortion correction circuit realized by geometric distortion correction circuits.
One disadvantage of the geometric distortion correction method of the prior art is the large circuit scale, and a major disadvantage is the attendant deterioration in image quality of the output image. Although it is typical to use this geometric distortion correction for correcting distortion when an image is projected onto a surface that is not planar, it is not effective to use the geometric distortion correction circuit for only correcting the distortion of the optics when projecting an image onto a planar screen.
In the electrical luminance correction method of the prior art, when, for example, a single image is divided vertically and a video signal then projected and displayed using two projectors, electrical gradation control is carried out at intervals of any fixed number of picture elements in the horizontal direction from the right and left edges of the display image, and as a result, when the two projectors have optical distortion, it was impossible to eliminate the conspicuousness of the uneven luminance of overlapping regions of white levels, as shown in FIG. 1 (4).